1. Field of the Invention
The present invention relates to a method of driving an x-ray detector and an x-ray detector using the same. More particularly, the present invention relates to an x-ray detector and a method of driving the x-ray detector in which image distortion caused by an offset voltage deviation is substantially reduced and/or effectively prevented.
2. Description of the Related Art
An x-ray detector is used, for example, as a medical diagnosis device which detects an x-ray image of an object photographed by an x-ray generator, to provide the x-ray image to a display device.
Recently, a flat panel detector which utilizes a digital radiography (“DR”) method has been widely used as an x-ray detector, since the DR method does not require film. A flat panel x-ray detector using the DR method typically includes a plurality of light detecting pixels in the flat panel detector to detect an x-ray incident thereon. Each light detecting pixel of the plurality of light detecting pixels includes a photodiode. The photodiode detects an x-ray emitted from an x-ray generator and outputs an electrical signal proportional to the x-ray. The light detecting pixel further includes a switching device which transmits the electrical signal output from the photodiode to a readout integrated circuit of the flat panel x-ray detector.
The readout integrated circuit reads out, e.g., receives, the electrical signal from the flat panel detector. Specifically, the readout integrated circuit reads out the electrical signal based on a gate voltage provided from a gate driver which sequentially turns on switching devices of associated light detecting pixels arranged in a row direction. Thus, the readout integrated circuit sequentially reads out electrical signals on a row basis.
The electrical signal is thereafter output from the readout integrated circuit and is processed in a controller, typically disposed on a main board. The electrical signal is thereafter converted to an image signal and transmitted to a display device to display the x-ray image thereon.
In general, when the x-ray is not provided to the flat panel from the x-ray generator, an electric potential at a coupling node (e.g., a node at which the photodiode and the switching device of a given light detecting pixel are connected) gradually changes based on a changing offset voltage of the photodiode. Further, when an input interval, e.g., a duty cycle, of the x-supplied ray from the x-ray generator is varied, an operation timing of the photo diode changes and, as a result, the offset voltage at the coupling node further varies.
As a result of the varying offset voltage at the coupling node, the electrical signal output from the photodiode is adversely affected. For example, a distortion in which the offset voltage is added to the electrical signal when the switching device is turned on may occur. To mitigate this problem, an offset compensation method which detects the offset voltage of the signal output from the switching device to remove the offset voltage from the electrical signal has been suggested. However, in the offset compensation method of the prior art, when the offset voltage varies based on the operation timing of the photo diode, as described above, it is difficult to perform the offset compensation method. As a result, a distorted image, caused by an offset voltage deviation based on the operation timing of the photo diode, is displayed on the display device of the x-ray detector of the prior art.